What this test measures
Anti-myeloperoxidase (MPO) antibodies target myeloperoxidase, an enzyme in neutrophil granules. On indirect immunofluorescence of ethanol-fixed neutrophils these antibodies produce a perinuclear pattern (p-ANCA — fluorescence around the nucleus). Confirmation is by quantitative MPO-specific ELISA.
MPO-ANCA is one of two main pathogenic ANCA antibodies. The other is PR3-ANCA, which produces the cytoplasmic (c-ANCA) pattern. Together they define ANCA-associated vasculitis (AAV) — a group of small-vessel vasculitides that can affect kidneys, lungs, ENT, skin and nerves.
Why it matters
MPO-ANCA is the primary serological marker for two conditions: microscopic polyangiitis (MPA), which often presents with rapidly progressive glomerulonephritis and alveolar haemorrhage, and eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss syndrome) which presents with adult-onset asthma, eosinophilia and vasculitic features. About 30–40% of granulomatosis with polyangiitis (GPA) patients are also MPO-ANCA positive.
In Indian rheumatology and nephrology practice, MPO-ANCA is essential in the workup of: rapidly progressive kidney failure with blood and protein in urine, unexplained pulmonary haemorrhage, peripheral neuropathy with systemic features, palpable purpura, and adult-onset asthma with eosinophilia. Early diagnosis is critical because untreated AAV has high mortality, but with prompt cyclophosphamide or rituximab + steroids, induction of remission is achievable in most patients.
How to prepare
No fasting required. Continue all medications. Note that immunosuppressants may lower ANCA titres but the test will still detect significant disease.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| MPO-ANCA IgG (U/mL)[1][2][3] | Negative: < 20 U/mL (assay-dependent) | Negative MPO-ANCA makes ANCA-associated vasculitis less likely but does not rule it out — a small proportion are ANCA-negative ("seronegative AAV") and PR3-ANCA may be the dominant antibody in others. | Positive MPO-ANCA supports microscopic polyangiitis, EGPA, or MPO-positive GPA. Higher titres usually correlate with active disease; rising titres can predict relapse. Drug-induced ANCA (cocaine, hydralazine, propylthiouracil, minocycline) is often MPO-positive at very high titres. |
MPO-ANCA vs PR3-ANCA — clinical correlations
| Feature | MPO-ANCA (p-ANCA) | PR3-ANCA (c-ANCA) |
|---|---|---|
| Most associated disease | Microscopic polyangiitis, EGPA | Granulomatosis with polyangiitis (GPA) |
| Kidney involvement | Very common | Common |
| ENT involvement (sinusitis, saddle nose) | Less common | Very common |
| Adult-onset asthma + eosinophilia | Common (EGPA) | Rare |
| Relapse rate | Lower (~30%) | Higher (~50%) |
| Drug-induced cause | Cocaine, hydralazine, PTU | Less common |
Frequently asked questions
Do I need to fast?
No fasting required.
Why are MPO-ANCA and PR3-ANCA done together?
Both are needed to classify ANCA-associated vasculitis. The pattern (p-ANCA vs c-ANCA) on immunofluorescence is confirmed by specific MPO or PR3 ELISA.
My MPO-ANCA is positive — does that mean vasculitis?
Strongly supports it in the right clinical setting (rapidly progressive kidney disease, lung haemorrhage, neuropathy). The diagnosis usually requires biopsy confirmation as well.
Can ANCA become positive from medications?
Yes. Cocaine (especially adulterated with levamisole), hydralazine, propylthiouracil, minocycline and certain biologics can cause drug-induced MPO-ANCA. Discontinuing the trigger often resolves the antibody and disease.
Does treatment lower the titre?
Yes. Effective immunosuppression usually lowers titres. Rising titres in a previously controlled patient can predict relapse and prompt closer monitoring.
How long does the report take?
Typically 2–4 days.
Should this be tested alongside anti-GBM?
Yes — patients with pulmonary-renal syndrome should have both tested. About 10–15% are "double positive" with a distinct disease course.
Related Autoimmune / Rheumatology tests
Tests commonly ordered alongside MPO - ANCA ( P - ANCA ), or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — ANCA Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — ANCA Associated Vasculitis · accessed 2026-05-30T00:00:00.000Z
- ACR/Vasculitis Foundation — AAV Guideline · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Labs — MPO Antibody · accessed 2026-05-30T00:00:00.000Z
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